This invention relates to an assembly and method for delivering and deploying an expandable stent by balloon inflation, particularly within a lumen of a body vessel by means of a catheter assembly. It may be used for deploying other balloon expandable medical devices also, such as filters, grafts and occlusion devices. More specifically, this invention relates to the provision of a novel stent securement body within the stent expanding balloon to enhance the securement of the stent or medical device to the catheter assembly during intraluminal delivery of the stent to a deployment site. In accordance with this invention, the stent securement body comprises a fugitive element of the apparatus.
Stents and stent delivery assemblies are utilized in a number of medical procedures and situations and as such, their structure and function are well known. A stent is a generally cylindrical prosthesis which is introduced via a catheter into a lumen of a body, such as a vessel, in a configuration having a generally reduced diameter and then expanded to the diameter of the vessel. In its expanded configuration, the stent supports and reinforces the vessel walls while maintaining the vessel in an open, unobstructed condition.
Both self-expanding and inflation expandable stents are well known and widely available. Self-expanding stents must be maintained under positive external pressure in order to maintain their reduced diameter configuration during delivery of the stent to its deployment site. Inflation expandable stents (also known as balloon expandable stents) are crimped to their reduced diameter about the delivery catheter, positioned at the deployment site, and then expanded to the vessel diameter by fluid inflation of a balloon positioned between the stent and the delivery catheter. The present invention is particularly concerned with delivery and deployment of balloon expandable stents.
In advancing a balloon expandable stent through a body vessel to the deployment site, the stent must be able to securely maintain its axial position on the delivery catheter.
In positioning a balloon expandable stent on the delivery catheter over the fluid expandable balloon, the stent must be crimped to closely conform to the overall profile of the catheter and the unexpanded balloon.
It is known to make use of a mounting body, positioned about the catheter and within the balloon to provide a seat for the crimped stent. The application of securement pressure to the mounting body component of a catheter assembly provides a good friction fit to the stent and ensures good contact between the stent and the underlying balloon, mounting body and catheter, as already known in the art. The desired diameter of the stent upon the application of securement pressure to the mounting body and crimping recoil is characterized as the "delivery diameter", because in this condition the stent can safely, reliably and securely be delivered to the pre-selected position within a body vessel. Instead of merely crimping the stent onto the balloon and the underlying catheter and relying on the bulk of the flaccid balloon to hold the stent on, according to the present invention, the mounting body serves as a mounting base.
There are two basic functions to a mounting body. 1) It provides solid underlying material to which to crimp the stent, and 2) it may be shaped or configured to create a mechanical interference fit against axial movement of the stent. However, the presence of the mounting body on the catheter limits the catheter profile or diameter when the balloon is deflated following stent implantation.